1. Technical Field
The disclosure is related to a driving device, and in particular to a light source driving device.
2. Related Art
Solid state light sources, such as light-emitting diodes (LED) and organic LEDs (OLED) have advantages such as small volume, long life spans, high reliability, no radiation or toxic substances such as mercury. Solid state light sources have thus become the focus of development in the most popular new greentech optoelectronic industry and are deemed to have the greatest potential to replace conventional fluorescent light tubes or incandescent light bulbs and become applied in the lighting market. Therefore, for a solid state light source driver, the ability to provide stable power for the solid state light source has become a basic requirement. Currently, for manufacturers related to solid state light sources, the increase in life spans of solid state light source drivers, reduction of costs, and reduction in sizes of integrated circuits have become hallmarks in their competition in aspects of technology and costs.
An LED has characteristics similar to those of a diode. A brightness thereof is proportional to a supplied current. However, a thermal characteristic of an LED is similar to that of a negative resistor. The higher the temperature, the lower the resistance. Therefore, when a constant voltage is supplied to the LED, an increase in temperature often leads to a drastic increase in an LED current, thereby damaging the LED chip. Therefore, in conventional driver designs, a constant current is generally used, so as to prevent overheating of the LED which would lead to short circuiting or breakage of the device.
However, in a conventional driver, an active switching device often bears all of a voltage stress of a power source. This not only increases power consumption but also reduces the life span. Furthermore, after an electrolytic capacitor used by a conventional driver is used for a prolonged period, an electrolyte therein easily dries out, thereby leading to rapid deterioration and damage of the electrolytic capacitor. This is the main reason why life spans of conventional LEE) drivers cannot be effectively increased.